The clarification will help, but I can't answer your question. I have never been to the Philippines though I will hopefully be there in September.
I don't think language is difficult to learn for adults. In fact, I would throw out "difficult" and replace that term with "time consuming." A child whom spends half the day exposed to Mandarin in the classroom is in a better position to learn the language than an adult whom spends an hour every other day in self instruction.
If the adult were able to go through the same instruction, then I believe the adult would actually pick up the language faster. Adults are very good at their day jobs. For children, education is their day jobs.
Mandarin, like any language, is more complex than English is some regards but easier in many others. I believe Mandarin speakers would have a more difficult time learning English than the other way around. Give Chinesepod a try, I bet you will find it is much easier than you thought. However, you may not have the time available to learn a new language.
Time is our biggest problem I think. So many adults are so busy. Even if we don't really have many things to keep us busy, we are great at inventing wasteful methods for keeping up the appearance of being busy. I am lucky to be able to set aside the time to keep up with changes of my chosen field of business let alone learn a new language.
I wonder how good those schools really are? What non academic qualities do they teach? I spent all my childhood rebelling against school and pissing off my instructors. Today I am still refusing to listen to others and carving my own path. I think that sort of quality is what makes America so strong.
